The hazards to public health and the environment which are posed by a variety of synthetic halogenated organic compounds are well known. Compounds such as polychlorinated biphenyls (PCB's), dibenzodioxins, dibenzofurans, dichlorodiphenyl trichloroethane (DDT), dieldrin, lindane and chlordane, as well as other halogenated pesticides, have been found to be persistent, environmentally toxic materials which require safe and efficient means of disposal. PCB's pose a particularly serious disposal problem. Once widely used as dielectric fluid additives in electrical equipment such as transformers and capacitors because of their excellent insulating properties, the use of PCB's in many applications has been banned by the U.S. Environmental Protection Agency owing to the cumulative storage of PCB's in the human body and the extremely high toxicity of PCB's. Thus, methods for the removal and/or destruction of halogenated organic compounds such as PCB's are required.
Various methods for the destruction or decomposition of halogenated organic compounds are known in the art. For example, the Peterson U.S. Pat. Nos. 4,447,541 and 4,574,013 disclose methods for decontaminating soil which is contaminated with halogenated organic compounds. The Peterson U.S. Pat. No. 4,447,541 discloses a process in which a reagent mixture of an alkaline constituent and a sulfoxide catalyst (DMSO) are intimately mixed with soil contaminated with PCB's. The reagent mixture affects a desorption of the halogenated contaminants from the soil and subsequently dehalogenates the contaminants. However, this process is disadvantageous in that the kinetics are relatively slow and therefore reduction of the PCB concentration to an acceptable level requires extended time periods ranging from weeks to months, the soil must be completely dry for the destruction to take place, large quantities of the reagent are required, and the sulfoxide catalyst may potentially transport contaminants prior to their destruction. The Peterson U.S. Pat. No. 4,574,013 discloses a process wherein a heated slurry of contaminated soil is treated with a mixture of an alkaline constituent and a sulfoxide catalyst. However, this process is similarly disadvantageous in that the sulfoxide catalyst may transport contaminants into living systems, and the sulfoxide catalyst produces odorous compounds when heated to high temperatures and decomposes into combustible byproducts under elevated temperature conditions. This process is also disadvantageous in that it requires large amounts of reagents.
The Rogers et al U.S. Pat. No. 4,675,464 discloses a method for the chemical destruction of halogenated aliphatic hydrocarbons, and more particularly a method for the chemical destruction of ethylene dibromide. An alkali metal hydroxide is dissolved in an ethylene glycol and the resulting product is reacted with the halogenated hydrocarbon. Rogers et al further disclose that the reaction temperature should be maintained at 30.degree. C. or less to maintain the reaction products in solution.
The Rogers et al copending application Ser. No. 07/350,425 discloses a method for the destruction of halogenated organic compounds in a contaminated medium wherein an aqueous solution containing from about 0.1 to about 20 weight percent polyethylene glycol is added to a contaminated medium. An alkali metal hydroxide is also added to the contaminated medium, and the contaminated medium is heated at a temperature and for a time sufficient to dehydrate the medium. The medium is further heated at a temperature of between about 100.degree. and 350.degree. C. for a time sufficient to effect destruction of the halogenated organic compounds, and an acid is added to the medium in an amount sufficient to provide the medium with a pH of from about 7 to about 9.
The Rogers et al copending application Ser. No. 07/515,892 discloses a method for the decomposition of halogenated organic compounds contained in a contaminated medium wherein an aqueous solution of an alkali metal carbonate or bicarbonate is added to the contaminated medium, and the medium is heated to a temperature between about 250.degree. and 400.degree. C.
The Pytlewski et al U.S. Pat. No. 4,400,552 discloses a method for the decomposition of halogenated organic compounds which employs a reagent comprising the product of the reaction of an alkali metal hydroxide with a polyglycol or a polyglycol monoalkyl ether, and oxygen. The Pytlewski et al U.S. Pat. Nos. 4,337,368 and 4,602,994 disclose similar methods of decomposing halogenated organic compounds. Additionally, the Pytlewski et al U.S. Pat. Nos. 4,430,208, 4,417,977, 4,460,797 and 4,471,143 also disclose methods for separation and/or decomposition of halogenated organic compounds. However, these methods are disadvantageous in that excess amounts of the alkali metal hydroxide and polyglycol reagents are required in order to obtain a homogeneous distribution throughout the contaminated material, for example soil, sediment, sludge or the like, which is treated. The Pytlewski et al U.S. Pat. Nos. 4,349,380 and 4,523,043 disclose the use of reagents made from an alkali metal or alkali metal hydroxide and a polyglycol or a polyglycol monoalkyl ether for removing metals from metal-containing materials and for decomposing organo sulfur compounds, respectively. Similarly, the Brunelle U.S. Pat. Nos. 4,351,718 and 4,353,793 disclose methods for removing polyhalogenated hydrocarbons from nonpolar organic solvent solutions by treating the contaminated solutions with a mixture of polyethylene glycol and an alkali metal hydroxide. These methods are similarly disadvantageous in that excess amounts of reagent are required.
Additional methods for removing and/or destructing halogenated organic compounds contained in contaminated materials are disclosed in the Howard et al U.S. Pat. No. 4,327,027, the Heller U.S. Pat. No. 4,483,716, the Mendiratta et al U.S. Pat. No. 4,663,027, the Meenan et al U.S. Pat. Nos. 4,685,220 and 4,793,937, the Rossi et al U.S. Pat. No. 4,761,221, the Zeff et al U.S. Pat. No. 4,792,407, European Patent Application No. 118,858, Chemical Abstracts, Vol. 82, No. 39620P (1975) and Kornel et al, Journal of Hazardous Materials, 12 (1985), pages 161-176. However, many of these and additional processes known in the art for the removal and/or destruction of halogenated organic compounds in contaminated materials are inadequate in view of the time required for acceptable levels of removal and/or destruction, the use of excessive amounts of various reagents, the use of expensive reagents, the production of toxic and/or combustible byproducts, and/or the failure to obtain desired removal and/or destruction levels. Thus, a need exists for improved, cost effective methods for the removal, reduction and stripping of non-halogenated compounds from and the dehalogenation of halogenated organic compounds in contaminated materials, which methods overcome the disadvantages of the prior art.